I think I see similar failures again like we saw in bug 1172343 :(
http://jenkins1.qa.scl3.mozilla.com/view/Bitbar/job/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/207/HTML_Report/
Traceback (most recent call last):
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_client-0.16-py2.7.egg/marionette/marionette_test.py", line 277, in run
self.setUp()
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/tests/python/gaia-ui-tests/gaiatest/tests/functional/system/test_privileged_app_video_capture_prompt.py", line 13, in setUp
GaiaTestCase.setUp(self)
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/tests/python/gaia-ui-tests/gaiatest/gaia_test.py", line 862, in setUp
self.device.start_b2g()
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/tests/python/gaia-ui-tests/gaiatest/gaia_test.py", line 663, in start_b2g
self.marionette.start_session()
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_driver-0.9-py2.7.egg/marionette_driver/marionette.py", line 1015, in start_session
self.session = self._send_message('newSession', 'value', capabilities=desired_capabilities, sessionId=session_id)
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_driver-0.9-py2.7.egg/marionette_driver/decorators.py", line 36, in _
return func(*args, **kwargs)
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_driver-0.9-py2.7.egg/marionette_driver/marionette.py", line 691, in _send_message
response = self.client.send(message)
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_transport-0.5-py2.7.egg/marionette_transport/transport.py", line 101, in send
self.connect()
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_transport-0.5-py2.7.egg/marionette_transport/transport.py", line 89, in connect
hello = self.receive()
File "/var/lib/jenkins/jobs/flame-kk-319.mozilla-central.nightly.ui.functional.non-smoke.1.bitbar/workspace/.env/lib/python2.7/site-packages/marionette_transport-0.5-py2.7.egg/marionette_transport/transport.py", line 73, in receive
raise IOError(self.connection_lost_msg)
IOError: Connection to Marionette server is lost. Check gecko.log (desktop firefox) or logcat (b2g) for errors.
I also saw it in smoke 2 of bitbar and I guess this also happens in other places.

(In reply to Oliver Nelson [:oliverthor] from comment #3)
> Could we modify the timeout on tests so they never take more than 5 minutes?
> It would at least reduce some of the time overhead created by this failure.
I don't understand what you mean. We should never get these kinds of failures in the first place. They are very disruptive.

With the test in the pull request I can reproduce it after it starts with the 2nd run in there. The first test takes something like 272413ms.
When this issue occurs, I see only this message appearing, repeatedly:
V/WLAN_PSA( 215): NL MSG, len[048], NL type[0x11] WNI type[0x5050] len[028

There was no change in Gaia between those builds, so there is only a Gecko changelog to look for.
It looks like this was caused by bug 1180596.
We had similar issues before, for which we filed bug 1172343. That corresponded to the regression range and fix range for Presentation WebAPI and disabling it.
It also makes me wonder if bug 1171827 would be there again, potentially.
Gary, can you take a look at this?

(In reply to Martijn Wargers [:mwargers] (QA) from comment #18)
> Hmm, perhaps this is a different issue, this is much easier to reproduce in
> all kinds of testing in the latest Flame build.
I filed bug 1198950 for this.